Liquid-liquid separations of multi-phase solutions like those used in the production of hydrogen peroxide (H2O2) present a number of problems including but not limited to: emulsions, long separation times, and large capital expenses.
Most hydrogen peroxide manufacturing plants work on hydrogenation and subsequent oxidation of anthraquinone (or anthraquinone derivatives/analogs) dissolved in organics, typically yielding approximately 10-15 g/L hydrogen peroxide at the end of an operational cycle.
FIG. 6 illustrates one current method of producing hydrogen peroxide generally comprising the steps of: (1) hydrogenating an anthraquinone solution; (2) filtering the hydrogenated working solution: (3) optionally degassing the system; (4) oxidizing the hydrogenated working solution forming an oxidized working solution containing dissolved hydrogen peroxide; (5) separating the hydrogen peroxide from the oxidized working solution using traditional water extraction methods (i.e. liquid-liquid extraction columns etc) forming a raw aqueous hydrogen peroxide solution (containing contaminants); (6) purifying the raw aqueous hydrogen peroxide solution to remove contaminants; (7) and optionally distilling the purified aqueous hydrogen peroxide solution. See, PCT Application PCT/SE97/02100, International Publication No. WO 98/28225, which is hereby incorporated by reference in its entirety. A number of similar hydrogen peroxide processes have been developed. See, also U.S. Pat. Nos. 6,596,884; 6,982,072; 5,071,634; and U.S. Patent Application No. US2006/0057057, all of which are hereby incorporated by reference in their entireties.
Almost all known commercial methods for producing hydrogen peroxide use traditional water extraction methods (i.e. use of extraction columns) to separate hydrogen peroxide from the organic working solution. In such systems, the water and organic phases inevitable intermix leading to contamination of the resulting aqueous hydrogen peroxide solution. In addition, working solutions are designed to stabilize the catalyst, anthraquinone (AQ) and the hydrogenated form anthraquinol, in the presence of aqueous hydrogen peroxide. The lost of expensive catalyst AQ in the water phase during conventional liquid-liquid extraction increases the cost of H2O2 production. Cross-contamination between the aqueous and organic phases has been a long standing problem in the production of hydrogen peroxide. This contamination requires extra purification steps which are time and cost intensive.
Generally, H2O2 also needs to be diluted to certain concentrations (e.g., 5-10%) before it is used. If an efficient in-situ process for producing hydrogen peroxide at its desired concentrations is developed, the energy required for distillation and transport could be avoided. An added cost factor is that current processes to produce hydrogen peroxide in centralized facilities require hydrogen peroxide to be concentrated up to 70% to decrease volume for transport. These concentrated solutions require specialized stainless steel vessels and containers for storage and transport. In situ production avoids the need for centralized production and the component specialized vessels.
There exists a need in the art for a new liquid-liquid extraction method for separating hydrogen peroxide from a working solution which overcomes some or all of the problems associated with current methods.